Single suture biological tissue aortic stentless valve

ABSTRACT

A semilunar stentless valve is constructed entirely of biocompatible material, and has a plurality of leaflets that are joined to form an annulus and coapt to form a one-way valve. The leaflets open fully to minimize obstruction. A narrow rim strip overlies commissures where the leaflets join and around a base of the valve. The valve is of a conical design, flexible, easy to fit and preserves the integrity of the coronary sinuses. The valves can be implanted with a single suture row, reducing implant time significantly.

BACKGROUND OF THE INVENTION

The present invention relates to a stentless valve bioprosthesisconstructed of single or multiple sections of biocompatible materialtissue to minimize coronary obstruction. The valve is implantable with asingle suture row.

Various stentless valves have been advanced. Tissue valves are typicallyused in those patients for whom long term anticoagulation iscontraindicated, or who may be difficult to maintain on anticoagulationtherapy. The stentless valves typically are constructed in a manner thatrequires a double row of sutures for fastening, one along an inflow edgeand one along an outflow edge, and require a substantial amount of timefor implanting.

Existing state-of-the-art valvular prostheses have one or more of theproblems of introduction of foreign tissue, physical obstruction, andimplantation trauma. The implantation trauma is accentuated when thereis extensive suturing, for example, two suture rows.

Stentless aortic valves presently on the market have had problemsbecause the valves have tall bodies, leading to obstruction of thecoronary ostia or coronary sinuses, requirements for double suture rows,and extended implant times.

SUMMARY OF THE INVENTION

The present invention relates to an aortic or pulmonary stentless valvepreferably constructed entirely of crosslinked biological tissue, whichminimizes obstructions and permits implantation with a single suture rowin significantly less time than that needed for implanting existingvalves. The valve preferably is constructed of a single or of multiplepieces of bovine pericardial tissue. In a preferred form, multiplesegments of tissue are formed in such a way to provide for completecoaptation of the valve leaflets to prevent regurgitation orinsufficiency, and to provide full valve opening to allow for a maximumeffective orifice area. The exterior of the valve is preferably conicalin shape, which aids in implantation and reliability. The conical shaperesults in the valve being larger in diameter at the outflow end than atthe inflow end.

The preferred form of the invention is an assembly of three leaflets ofbiological tissue that are attached to adjacent leaflets at thecommissure region, preferably through the use of tissue reinforcingcommissure posts and a separate reinforcing rim strip. The rim strip issutured on the exterior of the leaflets when it is used and provides asuturing reinforcement at the perimeter or base of the valve. Thesuturing used for constructing or assembling the valve is on, or in, noncritical areas of the tissue to enhance valve durability.

The biological commissure reinforcement posts or pads are sculpted to beapplied at each commissure by slipping over adjoining edge portions ofmating edges of the leaflets to strengthen the attachment and aid in thedistribution of stresses at the critical areas where the adjacent valveleaflets join. The rim strip preferably is a biological tissuereinforcement that has portions sutured to the posts and leaflet edgesat the commissural area of the leaflets, and sutured to the base edgesof the leaflets, forming the base ring of the valve. The rim strip is onthe outside of the leaflets, to provide reinforcement to the rim formedby the base ends of the leaflets, and thus aids in the attachment of thevalve to the patient's annulus. The double layer of tissue at the rimprovides a suture attachment site that is designed for strength. Thedesign is anatomical in that it resembles the human aortic or pulmonaryvalve for a close fit, and needs only a single suture row forimplantation. The low profile valve is short along the flow axis and ofminimal width, so it is anatomically easy to handle.

Trimming biological tissue or other biocompatible material to thedesired size and shape for constructing the valve can be done readily.The assembly of the valve parts requires minimal time, thereby reducingmanufacturing costs. The implantation is easily carried out insignificantly less time than that needed for existing prostheses.

Flexibility of the tissue leaflets and the reinforcement posts and rimin the commissure areas where the leaflets open and close permits a wideopening to thus reduce pressure drop across the valve once implanted.The valve leaflets are less prone to tear because of cushioning by thevalve parts. The conical design and the flexibility of the tissueleaflets also ensures satisfactory leaflet coaptation to reduce anyregurgitation or insufficiencies. Further, the fully flexible valve canbe used in most aortic or pulmonary valve pathologies. The attachmentrim fits all normal and abnormal annulus shapes for implantation.

The bovine biological aortic or pulmonary stentless valve of the presentinvention has an anatomical profile. The sewing cuff or rim is part ofthe leaflets and may include a reinforcing rim strip. It has a conicshape to be accommodated in most aortic or pulmonary geometries, andprevent valve insufficiency. The sewing area is easily penetratable witha needle, being no more than about 2 mm thick. The valve flexibilitypermits it to follow the contour of the patient's annulus, thusremaining beneath both coronary sinuses. The internal to externaldiameter ratio is excellent and better than present designs since thecuff or rim is not covered with fabric. The cuff or rim is an intrinsicpart of the leaflets and follows the patient's annulus.

The present valve preferably is all biological and does not havesynthetic material, such as a polyester cloth covering. The valve has alow commissural profile that simulates natural valve geometry. There isa need of only one suture row for implantation and while placing thesutures, the leaflets are preserved from needle injury since thecomponents are all fully in the surgeon's view. The valve cuff or rimmay be reinforced with a biological strip or tape without increasing thecuff or rim width or affecting the effective orifice area. The time ofsurgery is reduced significantly, and may be in the range of one-thirdto one-half of the implantation time required for existing valves. Thereduced profile of the valve provides a superior view for the surgeon.This, in turn, helps in reducing implantation time, injury to leaflets,valve misalignment and occlusion of the ostia. Further, the problemsassociated with occlusion of the coronary sinuses is avoided, since thepresent valve leaves the coronary sinuses substantially unobstructed.Thus, situations caused by occlusions of the coronary sinuses or ostiaare not likely to occur.

The valve can be offered with a specific holder, just as the existingreplacement heart valves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outlet end plan view of a stentless aortic valve madeaccording to the present invention;

FIG. 2 is an inlet end plan view of the valve of FIG. 1;

FIG. 3 is a side view of the valve of FIG. 1;

FIG. 4 is a flat layout of a biocompatible material leaflet used forconstructing the biological valve of the present invention;

FIG. 5 is a flat layout of a commissural biocompatible material postused for the assembly of leaflets shown in FIG. 4 into a valve;

FIG. 6 is a flat layout of a scalloped biological rim that is used forfinal assembly of the valve of the present invention;

FIG. 7 is a perspective view of three leaflets being assembled using thereinforcing posts shown in FIG. 5;

FIG. 8 is a further perspective view showing the valve of the presentinvention when the biological rim shown in FIG. 6 is placed around theleaflet assembly, just prior to suturing the components to make thevalves shown in FIGS. 1-3;

FIG. 9 is a perspective schematic representation of the valve of thepresent invention being implanted with parts broken away; and

FIG. 10 is a plan view of the valve of the present invention after ithas been implanted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1, 2 and 3 illustrate a biocompatible material prosthetic aorticvalve assembly 10 which is a valving element and which has an outflowend 13 shown in FIG. 1. While the invention is described in reference toaortic valves, the invention is applicable to semilunar valves,including the pulmonary valve. The valve assembly is made of threeleaflets 11A, 11B, 11C. A scalloped, narrow rim strip 12 may be suturedaround the periphery of the base of the valve assembly and along thecommissure regions of the leaflets.

The biocompatible material for the leaflets, rim strip and postsincludes both biological material or synthetic polymers which could beeither naturally occurring or artificially produced.

Biological tissue for use in this invention includes relatively intacttissue as well as decellularized or otherwise modified tissue. Thesetissues may be obtained from, for example, heart valves, pericardialtissue, dura mater, small intestine submucosa, fascia, skin or any othermembranous tissue. Preferably, the biological tissue is bovinepericardial tissue. The biological tissue is selected to have strengthand flexibility. The tissue for the leaflets, posts and rim is selectedto avoid thin spots. Generally, the biological tissue is composed ofcollagen-containing structures derived from a particular animal species,typically mammalian, such as human, bovine, porcine, equine, seal, orkangaroo, as well as engineered tissues. Engineered tissue typicallyinvolves repopulated matrices which can be derived from the tissuesmentioned above or synthetically fabricated. The biological tissue maybe fixed to cross-link the tissue and provide mechanical stabilizationby preventing enzymatic degradation of the tissue, although the matricesdo not necessarily need to be fixed. Glutaraldehyde is typically used tofix the material, but other fixation methods, such as epoxides, otherdifunctional aldehydes, or photooxidation can be used.

Synthetic, biocompatible materials for use in the prosthesis of thepresent invention include synthetic polymers as well as biologicalpolymers. Synthetic, biocompatible materials for use in the prosthesisinclude synthetic polymers as well as biological polymers. Syntheticpolymers include polyamides(nylon),polyesters,polystyrene,polyacrylates, vinyl polymers (e.g. polyethylene,polytetrafluoroethylene, polypropylene and polyvinylchloride),polycarbonate, polyurethane, polydimethyl siloxane, cellulose acetate,polymethyl methacrylate, ethylene vinyl acetate, polysulfone, andsimilar copolymers. Biological polymers include natural forms such ascollagen, elastin and cellulose or purified biopolymers such aspolyaminoacids or polysaccharides. All of these materials can be usedsingularly or in a combination thereof and can be molded or cast intothe selected forms or can be knit or woven into a mesh to form a matrix.

The size of the leaflets will depend on the size of the valve that needsrepair, and can be selected as desired by manufacturers. Because thevalve assembly has no stent, and is very flexible, valve size is capableof being formed to fit a wide range of orifice sizes and shapes.Preferably, the leaflets comprise bovine pericardial tissue.

FIGS. 4-6 show the preferred form of the invention in flat layout. Eachof the leaflets shown generally at 11 has a commissure mounting ear 18on each side. The leaflets 11A-11C are held together at each commissurewith a separate commissural post 22, also preferably made of bovinepericardial tissue, as shown in FIG. 5. Each post 22 has a slit 24 sizedto slip over two thicknesses of leaflets at the commissure of twoadjoining leaflets. The slit 24 permits sliding a post 22 over the edgesof two adjoining leaflets to the interior of the commissural mountingears 18 of the leaflets. The ears or edge portions 18 are positionedoutwardly from the commissure posts and fold flat against the posts 22on the exterior of the slits 24, as shown in FIG. 7. There are threesuch posts 22 used when a three-leaflet valve is to be assembled, one ateach commissure.

The rim strip 12 shown in FIG. 6 in flat layout is formed from a singlepiece of biocompatible material as described above, preferably bovinepericardial tissue, in a scalloped shape to provide for sutureattachment. The rim strip 12 has three scalloped rim strip portions32A-32C joined by commissure post cover sections 34A-34C between thescallops. The flat layout shown in FIG. 6 indicates the end scallop 32Cis terminated along a line 35, which will join with the line 36 at theleft-hand side of the figure when the rim strip 12 is formed into anannulus for assembling the valve.

To assemble the valve, the three leaflets shown at 11A, 11B and 11C arejoined to form an annulus with the ear portions 18 in contact with theedge or ear portions 18 of the next adjacent leaflet to form twothicknesses of tissue. As shown, ear portion 18A on one side of theleaflet 11A is contiguous with the ear portion 18B of the adjacentleaflet 11B (see FIG. 7). The slit 24 of one commissural post 22 is slidover the contiguous edge of the leaflets, with the ears 18A and 18B tothe exterior.

The opposite side ear portion 18A of leaflet 11A is placed contiguouswith one side ear portion 18C of the leaflet 11C, and preferably acommissural post 22 is slipped in place over the two thicknesses oftissue. The ear portions 18B and 18C on the opposite side of therespective leaflets that are not attached are then placed contiguous aswell and the third commissural post 22 is slid over the finalcommissure. Each one of the commissures, formed by joining the threeleaflets, is provided with a post 22, shown in position in FIG. 7. Theears 18A and 18B are shown after they have been folded back onto theside portions of the posts 22.

FIG. 8 illustrates the next step in assembly, when the rim strip 12 ispositioned so that each one of the reinforcement posts 34A, 34B, and 34Cis overlying the ears 18 and posts 22 at each of the commissures betweenadjacent valve leaflets. The scalloped portions of rim strip 12 rest onthe rounded base ends 14A-14C of the leaflets to form a second layer oftissue at the base or inflow end of the valve. The base ends of theleaflets may be used as a sewing cuff or rim, without the reinforcingrim strip 12.

The next step is to suture the scalloped shaped rim strip 12 to theleaflet and post assembly. The sutures pass through adjacent(underlying) portions of the biocompatible material forming the leaflets11, in particular the base ends 14A-14C and posts 22. In FIGS. 7 and 8,it can be seen that the junction of the leaflets with the posts 22 andreinforcement posts 34A-34C of the rim strip 12 form edges 37 thatextend upwardly. When the rim strip 12 is in place, it provides anencircling, shaping rim and the outflow ends or edges 42 of the leafletswill tend to move toward the center and contact each other so that theycoapt at the outlet or outflow end. The lower rounded base portions14A-14C of the leaflets extend around the inflow end and form animplantation cuff or base. The scalloped rim strip portions 32A, 32B and32C coupled with the exterior surface of the base portions 14A-14C forma double layer of biocompatible material at the site of the sutureattachment. All suturing of leaflets in the assembly of the valve isplaced in areas of low stress to enhance durability of the valve, suchas commissural areas 51 or outflow ends 42.

As shown in FIG. 3, the posts 34A, 34B and 34C of the rim strip 12 arealso sutured to the posts 22 and the ears 18 of the leaflets with asuture that overlaps the edges of the rim posts 34A-34C and overlap thecommissures to insure there is no leakage. The sutures around theperiphery of the commissural posts not only can loop over the edge, asshown at 40 but can be passed through the ears 18 to insure a seal atthe commissure. The rim strip portions 32A-32C are also sutured to theedges of the curved base portions 14A, 14B and 14C as shown at 43.

The outflow ends 42 of the leaflets 11A-11C have generally straightedges, which will move apart or open under pressure from the inflow endof the valve 10, to expand to the full diameter permitted by the threeleaflets. Upon any reverse flow or back pressure, the leaflets willclose tightly to avoid regurgitation at the inflow commissures, as shownat 45 in FIG. 2. The mating outflow ends of the leaflets will foldtogether for accommodating changes in valve diameter and continue toclose tightly.

The stentless valve of the present invention is preferably all tissue(biomaterial), so it is flexible and can be fitted into place in theannulus. However, it is within the contemplation of the invention to usesynthetic or biological polymers for all or a portion of the valve. Therim strip 12 provides a bounding reinforcement along the curved leafletbase ends 14A-14C. The leaflets can be made of one single piece or threeseparate pieces of the biocompatible materials described above(biological or engineered tissue, or biological or synthetic polymers).No synthetic sewing cuff is added. The same leaflet material serves as asewing cuff or rim which is reinforced by the rim strips portions32A-32C without decreasing effective orifice area. The ratio betweeninternal and external diameter is superior to existing valves becausethere is no requirement for a fabric sewing ring or cuff or a stent.

As shown in FIG. 9, the base of the valve prosthesis will be positionedinternally of the heart tissue forming the aortic rim 49 after necessaryexcising of the diseased valve, and complete decalcification of theheart annulus. The valve assembly 10 is made to have a conical shape.The annular diameter of the base is smaller (in models about 4 mm less)than the outflow end diameter, which makes valve stenosis orinsufficiency insignificant. The valve will fit in most pathologies ofthe aortic or pulmonary valve. The top half of the valve can be expandedbecause the valve leaflets have redundant coaptation.

The aortotomy has been completed and the natural valve leaflets excisedin FIG. 9. FIG. 9 shows the left coronary artery 53B and the rightcoronary artery 53A. As shown in FIG. 9 one may use an interruptedsuture, depending on the patient's annular tissue quality. These singlecommissural sutures are shown and these same sutures can be used forsuturing of the valve rim to the patient's annulus, using a singlesuture row. A single suture can be started between the commissure linesalong the biological rim 12, and the valve 10 is sutured into placeeasily. The suture used for implantation is illustrated at 46 in FIG. 9,which schematically illustrates the valve 10 positioned prior toimplantation and shows initial attachment to the heart aortic rim tissue50.

Since the prosthesis is preferably made entirely of tissue, and has nostent or artificial material sewing ring, it can be manipulated to fitmost semilunar valve pathologies. The suturing of the prosthesis cancommence generally at one of the commissures. The base end portions 14(including portions 14A and 14B) of the leaflets curve outwardly from avalve flow axis and form the base of the sewing rim so the inlet size ismaximized to increase the effective orifice area between the posts whichare sutured directly to heart tissue at the annulus, schematically shownin FIG. 9. The curved base end portions 14 of the leaflets provide asmooth flow profile. Since there is a double layer of biocompatiblematerial at the sewing rim of the valve, including the rim strip 12 andthe curved base end portions 14 of the leaflets, the valve 10 is securedreliably. Also curving the leaflets to form a base for the sewing rimaids in maintaining a low profile valve. The axial distance or lengthrequired for the sewing rim is greatly reduced. Also, in this valve, theposts at the commissures are narrower in width than other tissue valves.These features aid in achieving the advantages of reducing implantationtime, injury to leaflets, valve misalignment and occlusion of the ostia.

The posts 34A-34C support the commissures of the leaflets 11A-11Cwithout impinging or obstructing the right and left coronary sinuses.The tissue 50 forming the annulus can be sutured directly to theperimeter of the posts 34A-34C and rim portions 32A-32C with a singlesuture row. A continuous stitch, a set of interrupted sutures, or acombination, in a single row is used up around the post as shown at 55,over the top of each commissure region of the leaflets and then down toextend around the partially circular portions of the base of theleaflets where the attachment is directly to the heart tissue 50. Knots45 are made to anchor the suture segments (see FIG. 10).

Since the entire valve is made of a flexible biocompatible material,there is a full flow diameter at the aortic orifice at the inflow end,as can be seen in FIG. 2. There are no rigid parts to cause nooks orcrannies that can produce local stasis of blood that may lead tothrombus formation. Further, since there is no sewing cuff, healing cantake place directly between the implanted tissue and the body tissue,and this provides for less likelihood of failures of sutures. The valveis short along the flow axis and thus anatomically easy to handle.

As shown schematically in FIG. 10 the coronary sinus region aroundarteries 53A and 53B are not impinged by the valve 10 when implanted.

The inflow of blood into the valve will cause the leaflets 11A-11C toseparate fully, against the aortic wall, with no sharp edges, pockets orthe like, and the valve design insures that there is no interferencewith the coronary sinuses or ostia. Because the leaflets are flexiblebiocompatible materials, they will close to prevent reverse flow withvery little leakage. Thus the valve 10 closes with low diastolicpressure.

Using one suture row as shown at 55 in FIG. 10 provides betterhemodynamics and good durability. The single suture row does not impingeon the coronary sinuses or ostia. The valve 10 has an excellent interiorto exterior size ratio for better hemodynamics.

The stentless valve 10 is fully flexible and is thus easier to fit forimplant. The valve will conform to the shape of the annulus and lumen ofthe aorta without distending the patient's tissue or placing unduestress on the suture attachments. The valve mimics operation of thenatural valve when implanted.

The leaflets coapt easily to provide the one-way check valve, and theyopen fully to avoid restriction of outflow, with a low pressure drop.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A stentless valve prosthesis made entirely ofbiological tissue comprising a sheet form of biological tissue cut toprovide a plurality of leaflets, each leaflet having edges joined toedges of other leaflets to encircle a flow opening and form a flowpassage, the edges extending in a direction along the flow passage andoutflow ends of the leaflets being of size to coapt to form a valve, anda narrow rim strip of biological material sutured to the leaflets aroundan inflow end, the narrow rim strip having post portions extending alongcommissures formed where the edges of adjacent leaflets join, andoverlying and being sutured to the leaflets along the commissures. 2.The valve of claim 1, wherein the plurality of leaflets comprises threeleaflets to form a valve, the rim strip comprising a narrow rim oftissue along the inflow end, the leaflets having base peripheriessmoothly curved outwardly around a base at the inflow end.
 3. The valveof claim 1, wherein an outflow end of the valve has a larger diameterthan the inflow end to form a conical shape.
 4. A stentless valveprosthesis made entirely of biological material comprising a pluralityof leaflets having edges joined along commissures to encircle a flowopening and of size to coapt to form a valve, a separate commissure postsupporting leaflets joined at each commissure, a rim strip sutured tothe leaflets around an inflow end, the rim strip having a rim postportion extending along each commissure post and sutured to the leafletsand to the commissure posts where adjacent leaflets join.
 5. The valveof claim 4, wherein each commissure post has a slot in which matingedges of two adjacent leaflets are positioned, the rim post portionsbeing sutured to ends of the leaflets extending through the respectiveslot to an exterior of the commissure post.
 6. The valve of claim 4,wherein said commissure posts and rim post portions extend in thedirection of flow beyond edges of the leaflets at an outflow end.
 7. Thevalve of claim 4, wherein said leaflets are individually formed, andhave leaflet portions that extend to an exterior from the commissureposts, said leaflet portions being covered by the rim post portions whenthe rim post portions are sutured to the commissure posts.
 8. Astentless tissue valve prosthesis, comprising a plurality of threesubstantially identically constructed leaflets of biological tissue,said leaflets having outflow edges at outflow ends that aresubstantially straight, and inflow edges that are curved, each leafletbeing joined to two other leaflets along commissures extending from aninflow end to an outflow end, thereby forming an interior flow passage,the outflow ends of said leaflets coapting to prevent reverse flow, thecurved inflow edges of the leaflets forming a rim for attachment totissue, a reinforcing strip of biological tissue along the curved inflowedges of the leaflets on an exterior of the leaflets to form a suturereinforcement along the rim, and a separate strip of biological tissueat each commissure secured to hold adjacent leaflets forming thecommissures together, a periphery of the valve being defined by theleaflets and the separate strips at each commissure.
 9. A stentlesstissue valve prosthesis, comprising a plurality of three substantiallyidentically constructed leaflets of biological tissue, said leafletshaving outflow edges at outflow ends that are substantially straight,and inflow edges that are curved, each leaflet being joined to two otherleaflets along commissures extending from an inflow end to an outflowend, thereby forming an interior flow passage, the outflow ends of saidleaflets coapting to prevent reverse flow, the curved inflow edges ofthe leaflets forming edge portions for attachment to tissue, a pluralityof commissure posts, one for each commissure, each commissure postcomprising a post of biological tissue having a longitudinal slittherein, said slit being of size to receive two thicknesses of leaflettissue at a respective commissure, to form a commissure junction betweenthe leaflets, a rim secured to the edge portions of the leaflet andhaving rim post portions sutured to the commissure posts, the commissureposts and rim post portions being spaced apart so the leaflets are freeto move outwardly between the rim post portions.
 10. A stentless valveprosthesis comprising a plurality of leaflets having edges joined toencircle a flow opening and of size to coapt to form a valve havingcommissures formed where adjacent leaflets join, a tissue post suturedat each commissure, the leaflets having base portions curving outwardlyfrom a central axis between the commissures to form an inflow end, andthe base portions forming at least a part of a sewing rim for the valve.11. The stentless valve prosthesis of claim 10, wherein the tissue isbovine pericardial tissue.